Multi-Stimuli Operando Transmission Electron Microscopy for Two-Terminal Oxide-Based Devices.

The integration of microelectromechanical systems (MEMS)-based chips for in situ transmission electron microscopy (TEM) has emerged as a highly promising technique in the study of nanoelectronic devices within their operational parameters. This innovative approach facilitates the comprehensive exploration of electrical properties resulting from the simultaneous exposure of these devices to a diverse range of stimuli. However, the control of each individual stimulus within the confined environment of an electron microscope is challenging. In this study, we present novel findings on the effect of a multi-stimuli application on the electrical performance of TEM lamella devices. To approximate the leakage current measurements of macroscale electronic devices in TEM lamellae, we have developed a postfocused ion beam (FIB) healing technique. This technique combines dedicated MEMS-based chips and in situ TEM gas cells, enabling biasing experiments under environmental conditions. Notably, our observations reveal a reoxidation process that leads to a decrease in leakage current for SrTiO3-based memristors and BaSrTiO3-based tunable capacitor devices following ion and electron bombardment in oxygen-rich environments. These findings represent a significant step toward the realization of multi-stimuli TEM experiments on metal-insulator-metal devices, offering the potential for further exploration and a deeper understanding of their intricate behavior.

Towards chemically neutral carbon cleaning processes: plasma cleaning of Ni, Rh and Al reflective optical coatings and thin Al filters for free-electron lasers and synchrotron beamline applications.

The choice of a reflective optical coating or filter material has to be adapted to the intended field of application. This is mainly determined by the required photon energy range or by the required reflection angle. Among various materials, nickel and rhodium are common materials used as reflective coatings for (soft) X-ray mirrors. Similarly, aluminium is one of the most commonly used materials for extreme ultraviolet and soft X-ray transmission filters. However, both of these types of optics are subject to carbon contamination, which can be increasingly problematic for the operation of the high-performance free-electron laser and synchrotron beamlines. As an attempt to remove this type of contamination, an inductively coupled plasma source has been used in conjunction with N2/O2/H2 and N2/H2 feedstock gas plasmas. Results from the chemical surface analysis of the above materials before and after plasma treatment using X-ray photoelectron spectroscopy are reported. It is concluded that a favorable combination of an N2/H2 plasma feedstock gas mixture leads to the best chemical surface preservation of Ni, Rh and Al while removing the carbon contamination. However, this feedstock gas mixture does not remove C contamination as rapidly as, for example, an N2/O2/H2 plasma which induces the surface formation of NiO and NiOOH in Ni and RhOOH in Rh foils. As an applied case, the successful carbon removal from ultrathin Al filters previously used at the FERMI FEL1 using an N2/H2 plasma is demonstrated.

Evaluation of Surface Cleaning Procedures in Terms of Gas Sensing Properties of Spray-Deposited CNT Film: Thermal- and O2 Plasma Treatments.

The effect of cleaning the surface of single-walled carbon nanotube (SWNT) networks by thermal and the O2 plasma treatments is presented in terms of NH3 gas sensing characteristics. The goal of this work is to determine the relationship between the physicochemical properties of the cleaned surface (including the chemical composition, crystal structure, hydrophilicity, and impurity content) and the sensitivity of the SWNT network films to NH3 gas. The SWNT networks are spray-deposited on pre-patterned Pt electrodes, and are further functionalized by heating on a programmable hot plate or by O2 plasma treatment in a laboratory-prepared plasma chamber. Cyclic voltammetry was employed to semi-quantitatively evaluate each surface state of various plasma-treated SWNT-based electrodes. The results show that O2 plasma treatment can more effectively modify the SWNT network surface than thermal cleaning, and can provide a better conductive network surface due to the larger number of carbonyl/carboxyl groups, enabling a faster electron transfer rate, even though both the thermal cleaning and the O2 plasma cleaning methods can eliminate the organic solvent residues from the network surface. The NH3 sensors based on the O2 plasma-treated SWNT network exhibit higher sensitivity, shorter response time, and better recovery of the initial resistance than those prepared employing the thermally-cleaned SWNT networks.

Microscopical and microbiologic characterization of customized titanium abutments after different cleaning procedures.

AIM: To assess and characterize pollution micro-particles and bacterial growth on customized titanium abutments after steaming, ultrasonic and plasma cleaning treatments. MATERIALS AND METHODS: Thirty commercially available implant abutments, after customization, were randomly divided into 3 groups of 10 and cleansed by steam (considered as control group), ultrasonic cleaning (test group 1) and plasma of Argon (test group 2). For all specimens, SEM analysis and EDAX microanalysis were performed to count and characterize pollution micro-particles, both on the abutment surface and implant-abutment connection. For the control and test groups, mean values and standard deviations were calculated for number and density of micro-particles. Statistical differences were determined by one-way ANOVA with Scheffe multiple comparison test. The level of statistical significance was set at P ≤ 0.05. Additional microbiologic analysis was performed to detect bacterial contamination on the abutment surface. RESULTS: In the control group, the number of micro-particles on average was 117.5, and 14.1, respectively, on the abutment surface and connection. In the test groups, no pollution was revealed on the abutment (average of 1.09 and 1.13 spots, respectively, in test group 1 and test group 2) and connection (1.28 and 1.41, respectively, in test group 1 and test group 2). The analysis of variance (ANOVA) showed a statistically significant difference for all the variables examined. For each variable, at least one of the groups differs from the others. Scheffe multiple comparison test showed that all comparisons for every variables between the control group and both groups are significant, while there were some comparisons between test group 1 and test group 2 that were not significant. EDAX microanalysis identified micro-particles as residual of lubricant mixed with traces of Titanium and other metals. Microbiologic analysis demonstrated the presence of bacterial growth on the abutment surface only in the control group (111.5 ± 11.43 CFU/ml/implant-abutment as mean value). In the test groups, absence of growing microorganisms was found. CONCLUSIONS: This study confirmed that both plasma and ultrasonic treatments can be beneficially adopted for abutment cleaning process after laboratory technical stages, to supposedly favor soft tissue healing and implant-prosthetic connection stability.

Nanosculptured tungsten oxide: High-efficiency SERS sensor for explosives tracing.

The accurate and rapid identification of explosives and their toxic by-products is an important aspect of safety protocols, forensic investigations and pollution studies. Herein, surface-enhanced Raman scattering (SERS) is used to detect different explosive molecules using an improved substrate design by controllable oxidation of the tungsten surface and deposition of Au layers. The resulting furrow-like morphology formed at the intersection of the tungsten Wulff facets increases nanoroughness and improves the SERS response by over 300 % compared to the untreated surface. The substrate showed excellent reproducibility with a relative standard deviation of less than 15 % and a signal recovery of over 95 % after ultrafast Ar/O2 plasma cleanings. The detection limit for the "dried on a surface" measurement case was better than 10-8 M using the moving scanning regime and an acquisition time of 10 s, while for the "water droplets on a surface" scenario the LoD is 10-7, which is up to 2 orders of magnitude better than the UV-Vis spectroscopy method. The substrates were successfully used to classify the molecular fingerprints of HMX, Tetryl, TNB and TNT, demonstrating the efficiency of a sensor for label-free SERS screening in the practice of monitoring traces of explosives in the water medium.

Label-Free Measurement of CD63 Positive Extracellular Vesicles Using Terahertz Chemical Microscopy.

Extracellular vesicles (EVs) are small cellular organelles involved in intracellular signaling and cell-to-cell interactions. Recent studies suggested that exosomes may have potential applications in the diagnosis and treatment of cancer and neurodegenerative diseases. In this study, extracellular vesicles of the human nonsmall cell lung cancer cell line H1299 and the unlabeled antiCD63 antibody were imaged using a new label-free terahertz chemical microscopy (TCM) technique to detect changes in the terahertz wave amplitude. To verify the high specificity of the protein biomarkers and the sensitivity of the biosensor surface, we also confirmed the selective binding of the antibody to the antigen, bovine serum albumin, and cancer cells. We also performed real-time measurements of the interaction between EVs from the H1299 cell and the antiCD63 antibody, which showed that the amount of change in the terahertz intensity increased with increasing concentration and the time to saturation decreased. Finally, to reuse the used biosensors (sensing plates), plasma-oxygen cleaning was used, and the activity of the biosensor surface was confirmed by terahertz microscopy and atomic force microscopy and was found to be reusable after less than 3 min of cleaning. Consequently, terahertz chemical microscopy was able to detect the presence or absence of antigen-antibody binding and its reaction rate and binding strength.

An apparatus for plasma cleaning and storage of transmission electron microscopy specimens and specimen holders.

The transmission electron microscopy (TEM) specimen with thickness in nanometer scale is susceptible to hydrocarbon contamination and oxidation, and the specimen holder is also susceptible to contaminants, which would deteriorate the quality of TEM imaging and degrade the efficiency of TEM experiments. Conventional pretreatment devices often have limited functions and low practicability, which may cause problems for TEM specimens and holders. In this work, a multifunctional apparatus for plasma cleaning and storage of TEM specimens and specimen holders is developed based on the specific design of the vacuum joints. The apparatus includes a plasma cleaning system, holder storage station, and specimen storage station, which share the same vacuum system. The cleaning of hydrocarbon contaminants on the specimen and storage of the specimens and holders can be achieved simultaneously in this apparatus. TEM imaging and energy-dispersive X-ray spectroscopy (EDS) analyses of two treated specimens using the apparatus demonstrated that it could effectively remove hydrocarbon contaminants on the specimen. The holder storage station, used to preserve TEM holders in vacuum conditions, can also be modified as a specimen storage station by an appropriate design of the specimen storage platform, in which specimens are protected from water and contaminations. The designed apparatus not only robustly avoids damage to the ultrathin specimen and holders but also improves the working efficiency and reduces costs. These advantages could make our apparatus more appealing for the complement to the present commercial plasma cleaning and storage devices. HIGHLIGHTS: An apparatus for the pretreatment of transmission electron microscopy (TEM) specimens and specimen holders with three functions-plasma cleaning, holder storage, and specimen storage-was designed and fabricated. Using this single apparatus, the cleaning of hydrocarbon contaminants on the specimen and storage of the specimens and holders can be achieved simultaneously. The designed apparatus can not only robustly avoid damage to the ultrathin specimen and holders but also improve the working efficiency and reduce costs by adopting a single vacuum system. These advantages could make our apparatus more appealing for the complement to the present commercial plasma cleaning and storage devices.

Electroformation of Giant Unilamellar Vesicles from Damp Lipid Films Formed by Vesicle Fusion.

Giant unilamellar vesicles (GUVs) are artificial membrane models which are of special interest to researchers because of their similarity in size to eukaryotic cells. The most commonly used method for GUVs production is electroformation. However, the traditional electroformation protocol involves a step in which the organic solvent is completely evaporated, leaving behind a dry lipid film. This leads to artifactual demixing of cholesterol (Chol) in the form of anhydrous crystals. These crystals do not participate in the formation of the lipid bilayer, resulting in a decrease of Chol concentration in the bilayer compared to the initial lipid solution. We propose a novel electroformation protocol which addresses this issue by combining the rapid solvent exchange, plasma cleaning and spin-coating techniques to produce GUVs from damp lipid films in a fast and reproducible manner. We have tested the protocol efficiency using 1/1 phosphatidylcholine/Chol and 1/1/1 phosphatidylcholine/sphingomyelin/Chol lipid mixtures and managed to produce a GUV population of an average diameter around 40 µm, with many GUVs being larger than 100 µm. Additionally, compared to protocols that include the dry film step, the sizes and quality of vesicles determined from fluorescence microscopy images were similar or better, confirming the benefits of our protocol in that regard as well.

Hydroxyl-modified Nb4C3Tx MXene@ZnIn2S4 sandwich structure for photocatalytic overall water splitting.

Herein, a hydroxyl-modified MXene@ZnIn2S4 (Nb4C3Tx MXene@ZIS-OH) overall water splitting photocatalyst with a sandwich structure was prepared through an in-situ growth strategy and peroxyl plasma post-treatment. The Nb4C3Tx MXene@ZIS-OH exhibits outstanding catalytic performance, which generates the release rates of hydrogen (53.8 µmol g-1h-1) and oxygen (26.7 µmol g-1h-1) from the water under visible light irradiation. After four photocatalytic cycling, the photocatalytic overall water splitting activity of Nb4C3Tx MXene@ZIS-OH is still 95.9% of the initial activity, which indicates that Nb4C3Tx MXene@ZIS-OH exhibits excellent cycling stability. Notably, the Nb4C3Tx MXene@ZIS-OH achieves an AQY of 1.2% for the overall photocatalytic water splitting at 380 nm. The sandwich structure and matched heterointerface between high work function Nb4C3Tx MXene and ZnIn2S4 nanosheets promote the electron transport, inhibit the charge recombination, and separate the generated H2 and O2 with effectiveness. Importantly, the Finite-Difference Time-Domain (FDTD) simulation suggests the hydroxyl groups on the surface of ZnIn2S4 could increase the hydrophilicity of photocatalyst and capture the holes generated by photoexcitation, thereby promoting the separation of electron-hole pairs rapidly. This work presents a successful example of constructing overall water splitting photocatalysts by energy level regulation, structure design and functional group modification.

Evaluation of plasma cleaning as an approach for the preparation of soil minerals for forensic comparison by photon and electron microscopy.

Although organic material is often used for forensic analysis, a substantial portion of the data gathered for determination of common origin of forensic soil samples is the inorganic, mineralogical composition of the sample, which may be obscured by the presence of soil organic material (SOM). Traditionally, SOM is removed by acidic, alkaline, or peroxide digest, or by combustion, but these techniques risk the damage to or destruction of target minerals of interest. Low-temperature plasma ashing, on the other hand, removes organic materials by exposing them to plasma ions with high-kinetic energy, converting organics to easily removed volatile products (CO, CO2 , H2 O, or methane) while avoiding the thermal alterations caused by heat combustion. This study exposed grains of known mineral types to 20 min of a low-pressure O2 plasma generated by a 10 MHz frequency generator. Powder x-ray diffraction was chosen as an independent method to evaluate the minerals for chemical or structural changes caused by this ashing process. Side-by-side comparison of before and after diffractograms revealed minimal, if any, variation in the detected 2θ and subsequently calculated d-spacing: differences in d values were found to generally be less than 1%, and most were within Hanawalt Search Index uncertainties by no less than a full order of magnitude. Peak intensity changes were similarly minimal. This study strongly suggests that low-temperature plasma ashing can be used for the isolation of inorganic soil material fraction for forensic soil analysis with little or no concern for potential alteration of the mineral grains.